Cross-signing [1/4] -- hidden devices (#5759)

* allow devices to be marked as "hidden"

This is a prerequisite for cross-signing, as it allows us to create other things
that live within the device namespace, so they can be used for signatures.

4 files changed, 49 insertions, 10 deletions

diff --git a/changelog.d/5759.misc b/changelog.d/5759.misc
new file mode 100644
index 0000000000..c0bc566c4c
--- /dev/null
+++ b/changelog.d/5759.misc
@@ -0,0 +1 @@
+Allow devices to be marked as hidden, for use by features such as cross-signing.
\ No newline at end of file
diff --git a/synapse/storage/devices.py b/synapse/storage/devices.py
index 8f72d92895..991e28ea24 100644
--- a/synapse/storage/devices.py
+++ b/synapse/storage/devices.py
@@ -1,5 +1,7 @@
 # -*- coding: utf-8 -*-
 # Copyright 2016 OpenMarket Ltd
+# Copyright 2019 New Vector Ltd
+# Copyright 2019 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -20,7 +22,7 @@ from canonicaljson import json
 
 from twisted.internet import defer
 
-from synapse.api.errors import StoreError
+from synapse.api.errors import Codes, StoreError
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage._base import Cache, SQLBaseStore, db_to_json
 from synapse.storage.background_updates import BackgroundUpdateStore
@@ -36,7 +38,8 @@ DROP_DEVICE_LIST_STREAMS_NON_UNIQUE_INDEXES = (
 
 class DeviceWorkerStore(SQLBaseStore):
     def get_device(self, user_id, device_id):
-        """Retrieve a device.
+        """Retrieve a device. Only returns devices that are not marked as
+        hidden.
 
         Args:
             user_id (str): The ID of the user which owns the device
@@ -48,14 +51,15 @@ class DeviceWorkerStore(SQLBaseStore):
         """
         return self._simple_select_one(
             table="devices",
-            keyvalues={"user_id": user_id, "device_id": device_id},
+            keyvalues={"user_id": user_id, "device_id": device_id, "hidden": False},
             retcols=("user_id", "device_id", "display_name"),
             desc="get_device",
         )
 
     @defer.inlineCallbacks
     def get_devices_by_user(self, user_id):
-        """Retrieve all of a user's registered devices.
+        """Retrieve all of a user's registered devices. Only returns devices
+        that are not marked as hidden.
 
         Args:
             user_id (str):
@@ -66,7 +70,7 @@ class DeviceWorkerStore(SQLBaseStore):
         """
         devices = yield self._simple_select_list(
             table="devices",
-            keyvalues={"user_id": user_id},
+            keyvalues={"user_id": user_id, "hidden": False},
             retcols=("user_id", "device_id", "display_name"),
             desc="get_devices_by_user",
         )
@@ -540,6 +544,8 @@ class DeviceStore(DeviceWorkerStore, BackgroundUpdateStore):
         Returns:
             defer.Deferred: boolean whether the device was inserted or an
                 existing device existed with that ID.
+        Raises:
+            StoreError: if the device is already in use
         """
         key = (user_id, device_id)
         if self.device_id_exists_cache.get(key, None):
@@ -552,12 +558,25 @@ class DeviceStore(DeviceWorkerStore, BackgroundUpdateStore):
                     "user_id": user_id,
                     "device_id": device_id,
                     "display_name": initial_device_display_name,
+                    "hidden": False,
                 },
                 desc="store_device",
                 or_ignore=True,
             )
+            if not inserted:
+                # if the device already exists, check if it's a real device, or
+                # if the device ID is reserved by something else
+                hidden = yield self._simple_select_one_onecol(
+                    "devices",
+                    keyvalues={"user_id": user_id, "device_id": device_id},
+                    retcol="hidden",
+                )
+                if hidden:
+                    raise StoreError(400, "The device ID is in use", Codes.FORBIDDEN)
             self.device_id_exists_cache.prefill(key, True)
             return inserted
+        except StoreError:
+            raise
         except Exception as e:
             logger.error(
                 "store_device with device_id=%s(%r) user_id=%s(%r)"
@@ -584,7 +603,7 @@ class DeviceStore(DeviceWorkerStore, BackgroundUpdateStore):
         """
         yield self._simple_delete_one(
             table="devices",
-            keyvalues={"user_id": user_id, "device_id": device_id},
+            keyvalues={"user_id": user_id, "device_id": device_id, "hidden": False},
             desc="delete_device",
         )
 
@@ -604,14 +623,15 @@ class DeviceStore(DeviceWorkerStore, BackgroundUpdateStore):
             table="devices",
             column="device_id",
             iterable=device_ids,
-            keyvalues={"user_id": user_id},
+            keyvalues={"user_id": user_id, "hidden": False},
             desc="delete_devices",
         )
         for device_id in device_ids:
             self.device_id_exists_cache.invalidate((user_id, device_id))
 
     def update_device(self, user_id, device_id, new_display_name=None):
-        """Update a device.
+        """Update a device. Only updates the device if it is not marked as
+        hidden.
 
         Args:
             user_id (str): The ID of the user which owns the device
@@ -630,7 +650,7 @@ class DeviceStore(DeviceWorkerStore, BackgroundUpdateStore):
             return defer.succeed(None)
         return self._simple_update_one(
             table="devices",
-            keyvalues={"user_id": user_id, "device_id": device_id},
+            keyvalues={"user_id": user_id, "device_id": device_id, "hidden": False},
             updatevalues=updates,
             desc="update_device",
         )
diff --git a/synapse/storage/end_to_end_keys.py b/synapse/storage/end_to_end_keys.py
index 1e07474e70..6f524cedd9 100644
--- a/synapse/storage/end_to_end_keys.py
+++ b/synapse/storage/end_to_end_keys.py
@@ -85,7 +85,7 @@ class EndToEndKeyWorkerStore(SQLBaseStore):
             "    k.key_json"
             " FROM devices d"
             "    %s JOIN e2e_device_keys_json k USING (user_id, device_id)"
-            " WHERE %s"
+            " WHERE %s AND NOT d.hidden"
         ) % (
             "LEFT" if include_all_devices else "INNER",
             " OR ".join("(" + q + ")" for q in query_clauses),
diff --git a/synapse/storage/schema/delta/56/hidden_devices.sql b/synapse/storage/schema/delta/56/hidden_devices.sql
new file mode 100644
index 0000000000..67f8b20297
--- /dev/null
+++ b/synapse/storage/schema/delta/56/hidden_devices.sql
@@ -0,0 +1,18 @@
+/* Copyright 2019 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+-- device list needs to know which ones are "real" devices, and which ones are
+-- just used to avoid collisions
+ALTER TABLE devices ADD COLUMN hidden BOOLEAN DEFAULT FALSE;